Condition responsive control device with capacity for independent adjustment of control points

ABSTRACT

A control device wherein a pressure sensitive element displaceable by pressure variations, transmits linear motion to a balance plate. Stops associated with the balance plate define a pair of axes about which the balance plate alternately pivots. The device includes a single control such as a microswitch having a single actuator displaceable between first and second positions corresponding to mutually cancelling control modes. Pivotal movement of the balance plate about one axis effects movement of the actuator through the first position while pivotal movement about the other axis effects movement of the actuator through the second position. The pressures at which the respective positions are attained can be independently determined by adjustable springs acting on the balance plate and through the respective axes.

United States Patent 1191 Weber Jan. 15, 1974 [54] CONDITION RESPONSIVECONTROL 3,098,141 7/1963 Wintriss 200/153 W UX DEVICE W CAPACITY FOR3,303,306 2/1967 Fischer et al. 200/83 S 3,390,242 6/1968 gg N q fgggigfNlg 0F 3,182,150 5/1965 Smith 200/83 SA [76] Inventor: Ernesto JuanWeber, Lluvia 470, FOREIGN PATENTS OR APPLICATIONS State of the FederalDistrict, 1,263,541 7/1960 France 200/153 T Mexico E J R S Primaryxaminer cott v [22] Flled: 1972 Assistant ExaminerRobert A. Vanderhye211 App] 23 732 Att0rneyArthur Schwartz 7 Related US. Application Data[63] Continuation-impart of Ser. No. 154,536, June 18, [57] ABSTRACT1971 A control device wherem a pressure sensitive element displaceableby pressure variations, transmits linear [30] Foreign Application P i itD t motion to a balance plate. Stops associated with the May 31 1971Mexico 44155 balance plate define a Pair axes about which the balanceplate alternately pivots. The device includes a [52] CL H 200/83 R200/83 S 200/153 T single control such as a microswitch having a single337/323 actuator displaceable between first and second posi- 51 1111.C1. H0lh 35/34 ions Corresponding mutually cance'ling 58 Field of Search200/153 T 83 R m0des- Pivma] "Ovemenl of balance Plate about 200/83 s 83SA 83 J 82 R 82 5 one axis effects movement of the actuator through theQ 5 first position while pivotal movement about the other axis effectsmovement of the actuator through the sec- [56] References Cited 0ndposition. The pressures at which the respective positions are attainedcan be independently deter- UNITED STATES PATENTS 1 mined by adjustablesprings acting on the balance plate and through the respective axes.

3,210,486 10/1965 Holzer 200/81 R X 43 Claims, 9 Drawing FiguresPATENTEDJAN 15 m4 3. 786, sum 1 OF 4 212 FIG. 1

PATENTEUJAN 15 m4 sum 2 OF 4 mzminm 15 m4 3786 212 sum 3 er 4 CONDITIONRESPONSIVE CONTROL DEVICE WITH CAPACITY FOR INDEPENDENT ADJUSTMENT OFCONTROL POINTS CROSS REFERENCE TO RELATED APPLICATIONS This is acontinuation-in-part of US. application Ser. No. 154,536 by Ernesto J.Weber, filed on June 18, 1971.

BACKGROUND AND OBJECTS OF THE INVENTION 1. Field of the Invention Thisinvention relates to a control device, and, in par ticular, a controldevice in the form of a pressure switch. The device includes anexpansible chamber having a pressure sensitive element, such as adiaphragm, displaceable by variations in pressure. The pressuresensitive element actuates a control means, such as a microswitch, toproduce a control signal in response to the pressure variation.

In the present type of device, the pressure sensitive element is coupledto a balance means which in turn, is coupled to a pair of biasing meansor springs which urge the balance means in a direction opposingexpansion of the chamber. The resulting diaphragm displacement istransmitted to the balance means, causing the balance means to moveagainst the force of the weaker spring. This movement is a pivotalmovement about a first stop or abutment located opposite the weakerspring. The balance means is held against this stop by the heavierspring. The pivotal movement continues until the moving portion of thebalance means adjacent the weaker spring engages a second stop. At thispoint, the balance means is at the midpoint of its overall movement,further movement about the first stop being prevented by the secondstop. When pressure is sufficiently great to overcome the biasof theheavier spring, the balance means beings to pivot about the second stopuntil it reaches its extreme high pressure position.

As the pressure decreases from the extreme high pressure point, thebalance means will, of course, again pivot about the second stop, underthe bias of the heavier spring, but in the opposite rotational directionuntil the middle position is again reached. At the middle position, thebalance means is restrained by the first stop from further pivotalmovement about the second stop. When the pressure drops sufficiently,the balance means will again pivot about the first stop under the biasof the weaker spring. This movement continues until the balance meansreaches its extreme low pressure position.

The type of movement described above, and apparatus for effecting thesame, will hereinafter be referred to as alternating fulcrum movementand alternating fulcrum apparatus.

In many pressure switch applications, it is desirable to provide apressure differential between two different modes of actuation, forexample, an on mode and an off mode. The use of an alternating fulcrumdevice is ideal in this context for the movement of the balance meansabout one of the alternating fulcrums can control the on actuation ahdthe movement about the other other fulcrum can control the offdeactuation. Even more advantageous is the fact that the biasing meanscan be made adjustable to control the movement of the balance means andto concomitantly control the pressure values at which the switch isactuated or deactuated. Therefore, the use of an alternating fulcrumdevice having adjustable biasing means coupled to a balance means allowsindependent adjustment of the switch on and off points to practicallyany value in the overall operating range of the switch.

While the type of device contemplated has been and will be referred toas a pressure switch, it will be understood that the present inventioncan be equally well aapted to a vacuum responsive device, a temperatureresponsive device using a confined fluid, or a differential pressureresponsive device.

2. Description of the Prior Art The use of an alternating fulcrummovement per se in a pressure switch is known in the art.

U.S. Pat. Nos. 2,284,940; 2,266,144; and 2,274,119 to A.E. Baak alldisclose such devices. In these patents, as well as in all truealternating fulcrum devices, it is necessary that at least two stop orabutment means be disposed on opposite sides of the balance means fromeach other. The points of engagement of the stop means or abutments formthe fulcrums or axes about which the balance means pivots. Since thebiasing means must also be connected with at least one side of thebalance means, it becomes a problem to make the lines of action of thespring forces pass through the fulcrums or axes. This is true because,in the prior art devices, both the biasing means and the stop means oneside of the balance means will interfere with each other if located inthe same path. It is important that the forces of each of the biasingmeans pass through their adjacent fulcrums, because, if they do not,both biasing means will influence the movement of the balance meansabout each fulcrum. Since the separate springs are intended toindependently determine the different points of response, this influenceis detrimetnal to the proper functioning of the device. The firstabovementioned patent expresses the desirability of making the biasingforce act through the fulcrum, but examina tion of the disclosures inall the above patents makes it clear that the result sought after hasnot been achieved. In all three patents, the spring force acts at apoint offset from the adjacent fulcrum so that an undesirable,extraneous rotative force will always be exerted on the balance means.

In the first reference mentioned above, adjustment of the biasing meansis made from the same side of the unit as that on which the pressureinlet is located. Clearly, in many situations, this could makeadjustment difficult or impossible. The last two mentioned referencesabove provide for adjustment from positions spaced from the pressureinlet, but this is accomplished only through complex lever, linkage ortransmission systems which in turn account for large, bulky and complexunits.

US. Pat. No. 2,766,349 to Hamburg also discloses an alternating fulcrumpressure switch. An important drawback here is that the springs ofdifferent strengths are not adjustable and thus independent adjustmentof different settings is not possible. While it appears that, in anindirect manner, the biasing forces may be made to act through the pivotpoints of the balance means, the forces are transmitted throughmechanical means which clearly will introduce substantial friction, andthus extraneous forces will also be a problem here. Also, in Hamburg, itis necessary to use two microswitches, one at each end of the balancemeans, to obtain a substantial differential between actuation points.

U.S. Pat. No. 3,210,486 to Holzer discloses an alternating fulcrumdevice, or more precisely, an alternating axis device. The arrangementis such that the biasing forces do not act on the axes at all times.

'U.S. Pat. No. 2,790,044 to Booth discloses another device, which,broadly speaking might be considered to disclose movement about two axesto effect switch actuation. Here the biasing means is non-adjustable andacts on the balance means at a location clearly remote from the pivotingaxes.

OBJECTS OF THE INVENTION It is an object of the present invention toprovide a control device of the foregoing type of improved andsimplified construction, embodying relatively few operating parts andwhich can be built at a relatively low cost with a very compactconfiguration.

It is a further object of the invention to provide a control devicewherein at least two distinct control points can be made independentlyadjustable over a large range, and more particularly, a device which canprovide such adjustability when coupled with a single microswitch, orsimilar control means, having a single actuator.

It is another object of the invention to provide an alternating fulcrumor alternating axis control device having a pair of adjustable biasingmeans which act independently from each other.

It is an additional object of the invention to provide an alternatingfulcrum or alternating axis device wherein the lines of force of theadjustable biasing means act through the fulcrums or axes.

Another object is the provision of a connection and- /or linkage meansbetween the balance means and the microswitch or control means, whichlinkage and/or connection means is simple, reliable and economical andwhich comprises relatively few parts.

A further object of the invention is the provision of a simple,inexpensive lost motion means between the balance means and microswitchor control means to compensate for different ranges of displacement ofthe balance means and of the actuator of the control means.

Another object is the provision of an alternating axis device whereinthe axes nearly intersect at a pivotal set of stops, the effectiveconnection point of the balance means to the control means being at apoint on the balance means whereby the control means is not influencedby minute displacements of the balance means at the pivotal set ofstops.

Yet another object is the provision of a control device having a pistonand a diaphragm which are interconnected, and a means associated withthe diaphragm for eliminating friction betwen the piston and itsassociated cylinder.

Other objects and advantages will be apparent from or pointed out in thefollowing description and accompanying drawings.

SUMMARY OF THE INVENTION The present invention overcomes thedifficulties found in the prior art devices by providing an adjustablebiasing means whose lines of force act directly through each fulcrum oraxis of the balance means. In one embodiment, this is accomplished byproviding a balance means in the form of a beam with recessed portionsat each end. Each recess provides additional surfaces on the balancemeans whereby the stop means and biasing means may be aligned with eachother.

In another embodiment, the balance means takes the form of a plate whichpivots about two alternating axes, each axis being defined by stopswhich are spaced from each other. With this arrangement, it is possibleto locate the biasing means between the stops and yet position eachbiasing means so as to act directly on one axis. This latter arrangementhas the advantage of providing much greater stability and reliabilitythan can be obtained from a beam arrangement, and the added stabilitypermits the use of compression coil springs as biasing means.

Compression springs have the advantage that they can be most readilypositioned on the side of the balance plate opposite to the pressuresensing means and associated pressure inlet. Clearly, in mostcircumstances access to the switch will be easier from the side oppositethe inlet. Thus, with compression springs, adjustments to the springforces (and thus the response characteristics of the switch) can be madefrom the side opposite to the inlet. Also, when tension springs areused, mechanisms to permit rotation of the adjustment screws withrespect to their associated springs are required. With the use ofcompression srings, no such mechanisms are required, since the springsthemselves are free to rotate. The use of coil springs in cpmpression ismade more practical by the addition of special spring guides to preventbuckling.

Another important feature of the present invention is the fact that thestructural arrangement enables the use of a single, interchangeable,sensitive microswitch to obtain a large scale independent adjustment ofcontrol points. In all the prior art devices, it is necessary to use aplurality of microswitches coupled to opposite portions of the balancemeans for realization of the different actuating capabilities which canbe derived from an alternating fulcrum movement. Nowhere in the priorart is it realized that an alternating fulcrum movement can be used inconjunction with the inherent differential between distinct actuatorcontrol positions (e.g., on, off positions) of a conventional, sensitivemicroswitch to obtain widely and independently variable control pointsin terms of pressure. In other words, the almost microscopic fixeddifferential inherent in the microswitch is effectively made adjustableover a very large range by the mechanism of the present invention. Thisis accomplished by providing a single actuator, such as a push button,extending from the microswitch casing and operatively connected to thebalance means at a point between the two sets of stops exclusive of thepivotal set.

The above-described combination of a single microswitch, having a singleactuating button with an alternating fulcrum device, is facilitated byinterposing a resilient means between the balance plate and themicroswitch. The microswitch actuating button displacement will be verysmall when compared with the displacement of the pressure sensitiveelement or balance means. To facilitate the reduction of thisdiscrepancy, the resilient means is made sufficiently weak as to absorbsome of the movement of the balance means during its normal stroke.Thus, the resilient means provides an extremely simple, inexpensive lostmotion connection between the balance means and the control means whichis particularly suitable for use with the present type of alternatingfulcrum device. Any resilient means is subject to wear and this wearwould normally change the response characteristics of the pressureswitch. However, in an alternating fulcrum device, where on and offpoints are independently adjustable, any change in responsecharacteristics can readily be compensated.

Also, the fact that the actuating means is effectively connected to thebalance plate between the two sets of stops exclusive of the pivotal setprevents any substantial multiplication of vertical movement due tominute displacements of the balance plate at the pivot.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view, partly in sideelevation and partly in section, of a device according to one embodimentof the invention.

FIG. 2 is an exploded perspective view of most of the elements of thedevice of FIG. 1, certain elements being shown in section.

FIG. 3 is another exploded perspective view of the device of FIG. 1including elements not shown in FIG. 2.

FIGS. 4, 5 and 6 are fragmentary sectional views of the device shown inFIG. 1, these figures illustrating various displaceable elements atdifferent positions.

FIG. 7 is a fragmentary exploded perspective view of a modification tothe embodiment of FIG. 1.

FIG. 8 is a fragmentary sectional view of a modification to theembodiment of FIG. 1.

FIG. 9 is a view partly in section and partly in side elevation of adevice according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS Structural Description ofEmbodiment of FIGS. l-6

Referring to FIGS. 1-6, in the specifically illustrated embodiment ofthe invention, therexis shown a cylindrical housing 1 having a bottomend wall member 2 forming one wall of a sensing chamber 4. Another wallof the sensing chamber 4 is defined by a pressure sensing element hereinillustrated as a diaphragm 6. The diaphragm in effect divides thehousing into two chambers, namely, aforementioned lower sensing chamber4, and upper control chamber 5. The periphery of the diaphragm is heldin place, on one side, by a cylinder ring 8 secured to the housing 1and, on the other side, by an O-ring 10 which is pressed against thediaphragm by the bottom end wall member 2. The member 2 in turn, is heldin place in the housing by a snap ring 12.

While the pressure sensing means illustrated here takes the form of adiaphragm, any other suitable means such as a bellows or piston may beused.

A connection means 14, threaded to accommodate an appropriate conduit orfitting, communicates with a central passage 16 in the bottom end wallmember 2. The central passage 16, in turn, communicates with the sensingchamber 4.

The upper surface of the diaphragm 6 engages a piston 18 which moveswithin the cylinder ring 8. Abutment l5 prevents the piston from fallingout of its cylinder and functions as a lower limit to downward movement.The piston 18 is centered in the diaphragm by an annular convolution 20on the diaphragm formed by pressure when the device is in operation. Theconvolution 20 has a mean diameter slightly greater than the diameter ofthe piston and is shaped by pressure so as to engage the peripheral edgeportions of the piston to prevent lateral movement thereof. Theadvantage of such a piston centering arrangement is that it affords asimple means for avoiding friction between the piston and the cylinderring.

The housing includes an intermediate wall portion 22 which serves as anupper abutment to secure the cylinder 8 in place within the housing 1.In the center of the intermediate wall 22, is a bore 24 passingtherethrough and having a counterbore 25 at the upper surface of thewall 22. A pin 26 stepped in two diameters is disposed in the bore,larger diameter portion 27 being disposed within the counterbore 25. Atthe upper, large diameter portion 27 is a recess 28 which carries a ball29. The ball 29 defines a pivot about which the piston is free torotate, and this freedom of rotation facilitates formation of theconvolution 20 by pressure.

Adjacent the upper surface of the intermediate wall 22 there is disposeda shim 30 of spring-likg material having a symmetrical spider-likeshape. The shim includes an annular outerrim 31, symmetrically arrangedspokes 32 and a perforated inner hub 33. The outer rim 31 of the shim 30is held in place against the intermediate wall portion 22 by a lowerspace member 38, but the inner hub 33 is free to move vertically alongwith the pin due to the resiliency of the shim material and the reducedresistance resulting from the spoked configuration. Perforated hub 33 issuitably and firmly attached to a recessed portion 45 of a balance plate42, located above the shim.

The balance plate 42 has a generally disc-like configuration with alower surface 43 and an upper surface 44. The recess 45 has a centralball receiving part with a lower concave portion 34 and an upper convexportion 35. The lower concave portion engages the ball 29 of pin 26. Atpoints on the balance plate radially spaced from each other and near theperiphery thereof are located three balls or spherical members 46, 47and 48. Balls 46 and 47 are smaller than ball 48. Ball 46 protrudesdownwardly from the balance plate, and ball 47 protrudes upwardly.Preferably, the balls are so located with respect to each other as toform the points of an equilateral triangle. The balls may be securedwithin holes in the balance plate by staking or, alternatively, may beformed integrally with the balance plate. The open spaces between thespokes 32 of the shim 30 are aligned with the three balls so as topermit a direct contact thereof with the intermediate wall.

Above the balance plate is a ball stop plate 50 held in place by lowerspacer member 38. Also disposed above the balance plate 42 are a pair ofcoil springs 52,53 which are connected at their lowermost ends to springrests 54,55. The spring rests include annular shoulders 56,57 anddownwardly projecting fingers 58,59 at the lower portions thereof. Thesefingers 58, 59 engage complementary depressions 60,61 in the balanceplate to bias the plate downwardly.

The three balls 46, 47, 48 are arranged on the balance plate so as todefine a pair of axes A,B (see FIG. 2) about which the balance platealternately pivots. Each axis is defined by two points, each point beinga point of engagement of one ball with an adjacent sur face. The ballsare arranged so that the largest ball 48 i is common to both axes,locating one of the two points defining each axis. Ball 48 and theadjacent surfaces engaged thereby are referred to as the pivotal set ofstop means.

The ball stop plate 50 includes a central opening with curved cut outportions 62,63 for allowing the passage of the spring rests 54,55therethrough. The sectional view of FIG. 1 is taken through theseportions 62,63 so that the largest open area of the plate 50 isillustrated. The orientation of the balance plate 42 with respect to theball stop plate 50 is such that the balls 46,47 and 48 are not alignedwith the cut out portions 62 and 63. Thus, ball 47 will come intocontact with the ball stop plate 50 upon an upward pivoting movement ofthe balance plate 42. The largest ball 48 is of sufficient diameter toprevent any significant vertical movement thereof between the ball stopplate 50 and the intermediate wall 22.

The upper portion of the housing includes a top closure 66 having a pairof threaded openings 68,69 therein. A pair of threaded adjustment screws70,71 cooperate with these openings and with the coil springs 52,53 foradjusting the compression thereof. The adjustment screws each include atool engaging means 72,73 whereby each screw can be rotated to vary thevertical position thereof to adjust the associated spring. Eachadjustment screw includes a recess 74,75 at the bottom thereof, eachrecess receiving the uppermost portion of one of the coil springs 52,53.Each of the two adjustment screws includes an annular rim portion 76,77,one rim portion 77 being at the uppermost end of its respectiveadjustment screw 71, the other rim portion 76 being located below theuppermost portion of its adjustment screw 70. The spacing between thetwo adjustment screws 70,71 is such that the rim portions of each aremutually overlapping, the rim portion 77 being above the rim portion 76.By this arrangement, it is impossible to adjust the screw 71 to aposition below that of screw 70 or to adjust screw 70 to a positionhigher than screw 71. As the adjustment screw 70 is moved to arelatively lower position, it is clear that the compressive force on itsrespective coil spring 52 will be increased. Since the arrangement ofthe respective rims 76, 77 is such that the relative position of theadjustment screw 70 is always lower than or equal to that of adjustmentscrew 71, spring 52, associated with screw 70, is to be considered thehigh pressure spring in relation to the low pressure spring 53associated with the adjustment screw 75.

Secured above the top closure 66 is a control means 78, preferably inthe form of an electric, single pole, double throw, low differential,low force, two-position spring-return microswitch. Any suitableelectrical switch or fluid controlling valve of the spring-return ortoggle type could be used equally well, as long as there are providedtwo distinct actuation positions separated by a displacementdifferential, the positions corresponding to two distinct mutuallycancelling control modes. By way of example only, and for the sake ofconvenience, these two positions and their respective control modes arereferred to herein as the actuation or on position and the deactuationor off positions.

The microswitch here includes a casing. 79 from which extends anactuating button 82, having one position at which the switch is actuated(i.e., the on position) and another, different position at which theswitch is deactuated (i.e., the off position), so that an inherentdisplacement differential exists between the on and off positions.

The microswitch is fastened to the housing 1 by an adjustable mountwhich can be used to vary the vertical position of the microswitch withrespect to the housing 1.

In the illustrated embodiments, an actuating post 84 between theactuating button 82 and the balance plate 42 transmits only the linearvertical displacements of the balance means to the actuating button. Aresilient means 86 is also interposed between the actuating button andthe balance plate. This resilient means will be referred to as theamplification spring. In the embodiments of FIGS. 1-6, the amplificationspring 86 is attached to the upper surface 44 of the balance plate 42and is connected to the lower portion of the actuating post 84. Theamplification spring 86 is made sufficiently weak so as to serve as alost motion connecting means, reducing the amount of motion transmittedfrom the balance plate 42 to the actuation button 82 during the normalstroke of the balance plate and diaphragm. This reduction of transmittedbalance plate motion can be said to amplify the relative inherentdisplacement differential of the microswitch.

In an actual working model of a device according to the presentinvention, the piston moves through a stroke of approximately 0.006inches. At the same time the range of the microswitch button between onand off points is about 0.0005 inches to 0.0015 inches. Here theamplification spring provides a simple and inexpensive means tocompensate for these differences in displacement ranges.

The effective point of connection of the actuating post 84 to thebalance plate is located approximately midway on a straight line betweenthe two balls 46 and 47. Although, as illustrated, the actuating post 84first connects with the amplification spring which, in turn, isconnected with the balance plate 42, the post 84 may alternatively bedirectly attached to the balance plate (assuming the amplificationspring has a different location). In the embodiments illustrated, theeffective point of connection of the actuating post 84 with the balancemeans is the point at which the post 84 would engage the balance meansif extended downwardly past the amplification spring. It is desirable toplace the effective point of connection as close as possible to themidpoint of the line between balls 46 and 47. This in turn, assuresindependence of actuating post displacements with respect to minutebalance plate movements at the pivotal set of stops where both axesintersect ball 48. The aforesaid line between the balls 46 and 47 can beconsidered as a third axis (in addition to axes A and B) about which thebalance plate pivots during minute displacements of the balance means atball 48.

The provision of, on the amplification spring 86, a portion 87 whichextends away from the largest ball 48 (and thus away from the regionwhere the two axes nearly intersect), facilitates the placement of theeffective point of connection of the actuating means near the midpointof the line between balls 46 and 47.

The possibility exists, with the use of certain types of compressionsprings 52,53, that they may have a tendency to buckle causing a cockingor rotation of the spring rests 54 and 55. This undesirable occurrencecan be eliminated by providing elongated guide members 90 and 91surrounding and affixed to the spring rests 54,55. The guide member 90is secured at one end to the left hand spring rest (FIGS. I6) and at theother end to the part of the housing shown at the right. A similar butconverse arrangement exists for the guide member 91. This latter guidemember is secured to the right hand spring rest 55 and the left handportion of the housing.

When the spring rests move vertically due to balance plate displacement,the guide members rotate so that the ends nearest the spring rests movesubstantially vertically while the other ends remain secured in thehousing. Although, strictly speaking, the movement is arcuate, this isminimized by the fact that the elongation of the guide members 90,91 ismade as great as possible.

Both guide members 90,91 and the ball stop plate 50 are secured in placebetween an upper spacer 92 and the aforementioned lower spacer 38. Theends of the guide members can rotate inside of elongated cavities formedby recesses 117 and 118 in the upper spacer and the top surface of theintermediate wall 22. Alternatively, the guides may be fastened to thestationary housing by means of suitable flexible members.

A transparent plastic cover 94 is attached to the top closure 66 tocompletely enclose the microswitch 78 and adjustment screws 70 and 71 toprotect the same from dirt, dust or any other harmful materials in thesurrounding environment.

An opening 95 through the housing 1 and upper spacer 92 together with anopening 119 in the top closure 66 serves the purpose of providing apassage for the necessary connecting cables. Opening 95 is suitablythreaded for connection with a conduit.

Operation of Embodiment of FIGS. 1-6

The operation of the device illustrated in FIGS. 1-3 will be describedbelow, with reference being made to FIGS. 4, 5 and 6 showing variousdisplaceable elements in different sequential positions.

FIG. 4 illustrates the extreme low pressure position of the diaphragmand balance plate. In this position the balls 46 and 48 are held at restagainst the intermediate wall 22 by the force of the coil springs 52,53.Ball 47 is at an intermediate position and piston 18 rests on abutment15. As pressure in chamber 4 increases, the diaphragm and piston will bedisplaced upwardly. This upward displacement will be transmitted to thepiston 18 and thence to pin 26. The ball 29 transmits the motion of thepin 26 past the inner hub 33 of the flexible shim 30 and to the concaveportion 34 of the balance plate 42. The balance plate will first beginto move against the force of the weaker of the two coil springs, namely,spring 53, lifting ball 47. Meanwhile, the high pressure spring 52 willmaintain the ball 46 firmly in place against the intermediate wall. Theabove described movement of the balance plate, therefore, is acounterclockwise pivotal movement about axis A (defined by the points ofcontact of balls 46 and 48 with the intermediate wall 22).

Pivotal movement of the balance plate about the axis A will continueuntil the upper surface of the ball 47 comes into contact with the ballstop plate 50 to restrain further upward movement. At this point thebalance plate is disposed in the middle position as illustrated in FIG.5. The balance plate will remain in this position until the pressure inthe chamber 4 has increased to an amount sufficient to overcome the biasof the high pressure spring 52. At this point, the ball 46 is liftedfrom the intermediate wall and moves upwardly. To permit such movement,the balance plate pivots in a clockwise direction about the axis B(defined by the points of contact of balls 47 and 48 with the ball stopplate 50). Pivotal movement of the balance plate about axis B willcontinue until the extreme high pressure position shown in FIG. 6 isreached.

Upon decrease in pressure, the sequence of operations is precisely thereverse of that described above. With reference to FIGS. 5 and 6 thepivotal movement about axis B from the high pressure position of FIG. 6to the middle position of FIG. 5, as pressure decreases, is in acounterclockwise direction. After a decrease in pressure to a point atwhich the weaker spring 53 is able to overcome the upward force on thediaphragm, the balance plate will begin to return from the middleposition of FIG. 5 toward the low pressure position of FIG. 4, pivotingin a clockwise direction about the axis A.

It will be understood that, at all times when the balance plate pivotsabout the axis A, the line of force of the high pressure spring 52 willbe acting directly through that axis, so that the high pressure springis rendered ineffective, exerting no influence on the pivotal movementof the balance plate. Likewise, during movement of the balance plateabout the axis B, the low pressure spring 53 acts directly through thataxis and is rendered ineffective, exerting no influence on the pivotalmovement.

The above described alternate pivotal movements of the balance plateeffect only a linear displacement of the actuating post 84. The motionis transmitted from the balance plate to the actuating post 84 via theamplification spring 86 which serves as a lost motion connection. Thelinear movement of the actuating post is transmitted to the actuatingbutton 82 of the microswitch 78 for actuation and deactuation thereof.

As discussed above, there is an inherent displacement differentialbetween the position of the actuating button at which actuation of themicroswitch is effectuated and the position at which deactuation iseffectuated. This inherent differential between on and off points iscommon in known microswitches and other similar control means.

In the device of the present invention, the vertical position of themicroswitch 78 with respect to the housing 1 is adjusted so that themiddle position of the balance means, as illustrated in FIG. 5,corresponds to the middle position in the inherent displacementdifferential of the microswitch. In other words, with the balance platein its middle position, the microswitch actuating button is midwaybetween the actuation and deactuation points.

By way of example only, it will be assumed that the deactuation or offpoint of the microswitch corresponds to the vertically lower actuationbutton position in relation to the on point. As described above,assuming the balance plate to be in the low pressure position and themicroswitch in the off position, as pressure increases in the chamber 4,the balance plate 42 pivots about the axis A until reaching the middleposition. With sufficient additional increase in pressure, the balanceplate then begins to pivot about axis B. During this latter pivotalmovement, the post 84 will cause the button 82 to pass through theactuating position moving the switch to the on position.

As also described above, a pressure decrease causes the balance plate tomove back to the middle position by pivoting about axis B. Then, aftersufficient decrease in pressure, the balance plate begins to pivot aboutaxis A toward the low pressure position. During this latter pivotalmovement about axis A, post 84 causes the button 82 to pass through thedeactuation point moving the switch to the off position.

It will be understood that the values of pressure at which themicroswitch is moved into the on and off positions are determined by theadjustments to the biasing forces of the springs 52,53. To obtain a verywide pressure differential between on and off points, the high pressurespring 52 is adjusted to exert a very high biasing force. This isaccomplished by moving the adjusting screw 70 to a relatively lowposition. At the same time, the low pressure spring 53 is adjusted toexert a relatively weak biasing force by moving the adjusting screw 71to a relatively high position. With such an adjustment, assuming all theelements to be in their extreme low pressure positions, a very smallincrease in pressure causes the balance plate and microswitch button tomove into their middle positions at a very low pressure. The balanceplate and switch button remain in this middle position over a largerange of pressure increases until the pressure reaches a value near themaximum. At this high pressure, the force of the high pressure springwill finally be overcome to actuate the microswitch.

With only a small pressure drop, the balance plate and switch buttonagain return to their middle positions but the microswitch remains inthe on condition. After a large pressure drop to a point near theminimum pressure, the balance plate begins to pivot from itsintermediate position toward its low pressure position for deactuatingthe microswitch to the off condition.

It will be clear that a setting of the adjustment screws, whereby littledifference exists between the bias on the low pressure and high pressuresprings, creates a condition wherein the balance plate remains in theintermediate position only during a very small pressure change. Withthis condition, therefore, the pressure differential between on and offpositions of the microswitch is likewise very small. Also, it will beclear that, by adjustment of the biasing force on the springs, the highpressure on point and low pressure off point can be adjusted topractically any point within the overall range of operation of thedevice.

Modification According to FIG. 7

FIG. 7 shows an alternative embodiment wherein the ball stops, ratherthan being secured to the balance plate, are located separatelytherefrom. Whereas, in the previously discussed embodiment, the completestop means included the combination of the three balls on the balanceplate, plus the lower, intermediate wall 22, plus the upper, ball stopplate 50; the complete stop means in the present embodiment includes thebalance plate itself plus a set of balls adjacent both the upper andlower faces of the balance plate. Whereas in the previously describedembodiment, movement of the balance means caused the balls thereon toalternately come into contact with the intermediate wall and ball stopplate, in the arrangement of FIG. 7, the balance plate itself comes intocontact with stationary balls disposed on either side thereof. In theembodiment according to FIG. 7, elements which are substantiallyidentical with the corresponding elements in FIGS. 1-6, are indicated bythe same reference numerals. It is to be noted that, in FIG. 7, the wall22 is shown as a separate part rather than as an element which isintegrally formed with the housing, as in the previously describedembodiment.

In FIG. 7, a set of three balls or spherical members 101, 102 and 103are located in corresponding holes of a ball guide 108. The balls areheld in place both by the ball guide 108 and the intermediate wall 22located therebelow.

Balls 101, 102 and 103 together with guide 108 are disposed below theshim 30 and balance plate 42. When the balance plate is in its extremelow pressure position, it will rest against all three balls 101, 102 and103.

Disposed above the balance plate are two additional balls or sphericalmembers 110 and 111 located in holes in an upper ball guide 114.Directly above the guide 114 is the ball stop plate 50. Both the upperball guide 114 and ball stop plate 50 are effective to hold balls 110and 111 in their proper positions. The upper ball guide 114 includes cutout portions 115 and 116 substantially identical to, and aligned with,the corresponding cut out portions 62,63 of the ball stop plate 50.These cut out portions permit passage of the spring rests 54,55therethrough so that the fingers 58,59 thereof may engage depressions60,61 of the balance plate 42. The balls 111 and 102 are alignedvertically with each other and are so spaced from each other as topreclude any substantial vertical movement of the balance plate 42therebetween. The function of the balls 111 and 102, together, isanalogous to that of ball 48 in the previously described embodiment.Each of the alternating axes, shown as A and B in FIG. 7, pass throughthe vertical line between balls 102 and 111.

Ball 101 serves merely as a stop or rest for the balance plate 42 whenit is in its low pressure position. Ball 103 also serves this purpose,but, in addition, also serves to partially define the axis A about whichthe balance plate pivots during the initial stroke of the diaphragm. Theaxis A is fully defined by the points of engagement of the balls 102 and103 with the balance plate. The fact that the shim 30 has spokes 32between the outer rim 31 and hub 33 permits the balls 10], 102 and 103to protrude through the open spaces between the spokes and engage thebalance plate.

The pivotal axis B is defined by the points of contact of balls 110 and111 with the upper surface 44 of the balance plate 42. Ball 111 islarger in diameter than ball 110 and it may continuously engage thebalance plate at all times (but it is also possible that a very smallclearance may, at times, exist).

Operation of Modification According to FIG. 7

In operation, assuming that the balance plate is at its extreme lowpressure position and is held against balls 101, 102 and 103 by theforce of springs 52,53, an increase in pressure will cause the balanceplate 42 to be lifted against the bias of the low pressure spring 53.The balance plate 42 will move vertically upwardly away from ball 101while pivoting about the axis A. This movement continues until the uppersurface of the balance plate comes into contact with ball 110, which isvertically aligned with ball 101. At this point further pivotal movementabout the axis A is prevented. With a sufficient additional increase inpressure to overcome the force of high pressure spring 52, pivotalmovement about the axis B will commence. This movement will continueuntil the extreme high pressure position is reached. Movement from thehigh pressure position to the low pressure position upon decrease ofpressure is precisely the reverse of that described above.

In the embodiment of FIG. 7, the operation of remaining elements is thesame as that of the corresponding elements of the embodiment of FIGS.16. Modification According to FIG. 8

FIG. 8 shows a modification to the balance plate and ball arrangement ofFIGS. 1-6. Rather than providing a single ball 48 staked into thebalance plate so as to extend from both the top and bottom surfacesthereof, balls 120 and 121 are provided on either side of a simplechambered hole 124.

The use of balls, as elements .of the complete stop means in all .of theabove-described embodiments, is highly advantageous, since balls can beeasily manufactured to very close tolerances. This is important here,where the displacements involved are very small. Also, the fact thatmetal balls can easily be hardened is important where, as here, theywill be subjected to considerable wear.

Embodiment According to FIG. 9

FIG. 9 illustrates an additional embodiment of the present inventionutilizing a beam 150 in place of the balance means 42 of the previouslydescribed embodiments. Here, tension springs 152, 153 are used in placeof the compression springs 52,53 of the other embodiments. The same typeof microswitch 78 and actuating button 82 therefor are used with thisembodiment. As in the embodiments of FIGS. l-8, a pressure connection 14communicates with a chamber 4 defined by a bottom end wall 2 and adiaphragm 6. The diaphragm is attached to a piston 18 which in turn isconnected to an elongated vertical rod 155 engaging the central portionof the balance beam 150. Each end of the balance beam includes recessedportions 158 and 159, each recessed portion being effective to provide apair of downwardly facing surfaces 160 and 162, 163 anc 165 at itsrespective end. Tension coil springs 152 and 153 are connected near theends of the balance beam adjacent the lowermost of the downwardly facingsurfaces 162,165 at each end. The uppermost of the downwardly facingsurfaces 160,163 are adapted to engage with stop means 168,169 securedto the housing.

Tension spring 153 is adjusted to be the low pressure spring and tensionspring 152 is adjusted to be the high pressure spring. The arrangementis analogous to that of compression springs 52 and 53 of the embodimentspreviously described. An additional stop 171 is located on the side ofthe balance beam to which low pressure spring 153 is attached and ispositioned to engage an upwardly facing top surface 173 on the balancebeam. The arrangement of the springs and stops is such that, on each endof the balance beam, the line of force of the respective tension springcoincides with the point or points of contact of the respective stop orstops with the corresponding surface or surfaces of engagement on thebalance beam.

In the same manner as the balls and their respective surfaces of contactformed points defining the alternating axes of the embodiments of FIGS.1-8, the points of contact of the stops 168 and 171 with the surfaces160 and 173 define the fulcrum points about which the balance beam 150alternately pivots.

Operation of Embodiment of FIG. 9

The operation of the device of FIG. 9 is as follows.

Assuming the diaphragm 6 is in its extreme low pressure position, thedownwardly facing surfaces 160 and 163 will rest against stops 168 and169. As pressure increases and the diaphragm moves upwardly, surface 163of the balance beam will be lifted off stop 169 against the resistanceof the low pressure spring 153. At the same time the surface 160 will beheld against stop 168 by the bias of high pressure spring 152 so thatthe balance beam pivots about the fulcrum defined by the point ofcontact of surface 160 and stop 168. This pivotal movement continuesuntil the surface 173 engages the stop 171, at which point the balancebeam is in its middle position. When the pressure increases sufficientlyto overcome the tension of high pressure spring 152, the balance beamwill begin to pivot about the fulcrum defined by the point of contact ofstop 171 and surface 173. This pivoting movement continues until thehigh pressure position is reached. From this position the reversealternating fulcrum movement takes place as the pressure decreases andthe balance beam returns toward the low pressure position illustrated inFIG. 9.

It will be appreciated that the stops 168 and 171 define the fulcrumpoints for the alternating pivotal movement of the balance beam. It willbe further appreciated that these fulcrum points are aligned with theline of force of the adjacent tension spring. In this way, the springadjacent a given fulcrum is rendered completely ineffective duringrotation of the balance beam about that fulcrum. Therefore, similarly tothe situation in the other embodiments, the individual springs 152 and153 operate completely independently of each other.

It will be understood that in the embodiment of FIG. 9, the operation ofthe microswitch with respect to the movement of the balance beam isidentical to the operation thereof with respect to the movement of thebalance plate 42 in the other embodiments. Thus, the device illustratedin FIG. 9 possesses the same capabilities of full-scale independentpressure differential and pressure range adjustment.

Overpressure Protection In none of the embodiments of the presentinvention, has there been illustrated or described a stop or abutment torestrain the pivotal movement of the balance means as it approaches itsextreme high pressure position. It is intended that the position atwhich piston 18 contacts the intermediate wall 22 is to be consideredthe extreme high pressure position. Thus, in the event that the deviceis subjected to overpressures, the piston 18 and wall 22 will be able towithstand the forces thereof. If, on the other hand, a stop meansassociated with the balance means were to define the high pressureposition, a significant overpressure in the chamber 4 could result inserious damage to the balance means.

In the embodiment of FIG. 2 this possibility of damage is prevented byhaving ball 46 protrude downwardly, leaving sufficient space between thebalance plate and stop plate 50. In the embodiment of FIG. 7, the sameresult is obtained by the absence of a ball above the balance plate atthe left hand, high pressure side. In FIG. 9, the override protection isobtained by the absence of a stop above the balance beam near the upperhigh pressure side.

Fixed Differential It is possible to convert the pressure switch of thepresent invention to operate as a fixed differential device. In such adevice the displacement difference between the on and off points isrelatively constant but the overall pressure range may be adjustable.

In the embodiments of FIGS. 1-8 this is accomplished by elimination ofthe low pressure spring 53, its associated adjustment screw, spring restand guide. With such an arrangement, a negligible pressure will causethe balance plate to move into the middle position of FIG. 5. Thisconstitutes the low pressure position, and any substantial variations inpressure will cause the balance plate to pivot about the axis B. Theposition of the microswitch is adjusted so that both the actuation anddeactuation to and from the on and off points takes place entirelyduring the pivotal movement of the balance plate about axis B.

The same result is obtained in the device of FIG. 9 by eliminating thelow pressure spring 153 and its associated adjusting screw. Hereactuation and deactuation takes place during the pivotal movement aboutstop 171.

While throughout the above description words such as vertical", upper,"lower, upwardly, downwardly, right and left have been used, it will beunderstood that these terms are used only to describe relativerelationships and are not intended to be limiting. It will also beunderstood that those skilled in the art may make many changes andmodifications to the above-described embodiments of the presentinvention without departing from the spirit and scope thereof.

What is claimed is:

l. A control device comprising:

a. a housing;

b. a chamber in said housing;

c. a sensing means defining a wall of said chamber, said sensing meansbeing displaceable through a stroke;

d. a balance means having first and second sides, said sensing meansbeing operatively coupled to said balance means;

e. stop means associated with both said first and second sides of saidbalance means to define first and second axes about which said balancemeans pivots;

f. a pair of biasing means, at least one of which being adjustable andeach having a line of force acting on said balance means, said biasingmeans being positioned with respect to said balance means such that theline of force of one of said pair passes through said first axis at allpositions of said balance means and the line of force of the other ofsaid pair passes through said second axis at all positions of saidbalance means;

g. a control means operatively coupled to said balance means;

h. whereby displacement of said sensing means through one part of itsstroke effects pivoting of said balance means about said first axis anddisplacement of said sensing means through another part of its strokeeffects pivoting of said balance means about said second axis.

2. A control device as defined in claim 1 wherein both biasing means ofsaid pair are adjustable.

3. A control device as defined in claim 1 wherein:

a. said balance means is a balance plate;

b. said stop means includes a first portion and a second portion;

0. said stop means of said first portion includes a plurality of stopsspaced apart from each other to define said first axis; and

d. said stop means of said second portion includes a plurality of stopsspaced apart from each other to define said second axis.

4. A control device as defined in claim 3 wherein:

a. said first portion of said stop means is associated with said firstside of said balance plate; and

b. said second portion of said stop means is associated with said secondside of said balance plate.

5. A control device as defined in claim 1 wherein said 10 control meansis a microswitch.

LII

6. A control device as defined in claim 5 wherein said microswitch is asingle pole, double throw microswitch.

7. A control device as defined in claim 1 wherein:

a. said housing has first and second ends;

b. an inlet means communicates with said chamber, said inlet means beingdisposed in said first end; and

c. an adjusting means is disposed at said second end and is accessiblefrom the exterior of said housing.

8. A control device as defined in claim 1 wherein each of said biasingmeans is elongated, the longitudinal axis of one of said biasing meanspassing through said first axis, the longitudinal axis of the other ofsaid biasing means passing through said second axis.

9. A control device as defined in claim 1 wherein said stop meansinclude:

a. a plate disposed in said housing above said balance means;

b. a wall disposed in said housing below said balance means;

c. a plurality of protrusions extending from both said first and saidsecond sides of said balance means, said protrusions from said firstside being adapted to engage said wall, said protrusions from saidsecond side being adapted to engage said plate.

10. A control device as defined in claim 9 wherein said protrusions areformed by a plurality of spherical members, some of which have a firstpart extending from said first side of said balance means and others ofwhich have a second part extending from said second side of said balancemeans.

11. A control device as defined in claim 10 wherein said balance meansincludes a plurality of holes in which said spherical members areaffixed, whereby parts of said spherical members extend outwardly fromsaid balance means.

said stop means include:

a. a first set of protrusions disposed in said housing apart from andbelow said balance means, said first set being adapted to engage saidfirst side of said balance means; and

b. a second set of protrusions disposed in said housing apart from andabove said balance means, said second set being adapted to engage saidsecond side of said balance means.

14. A control device as defined in claim 13 wherein said protrusions areformed by spherical members.

15. A control device comprising:

a. a hollow housing;

b. a sensing means displaceable through a stroke, said sensing meansdividing said housing into a sensing chamber and a control chamber;

c. a balance means in said control chamber operatively connected to saidsensing means;

d. a plurality of stop means co-operating with said balance means todefine a pair of axes about which said balance means pivots;

e. a pair of adjustable biasing means coupled with said balance means,said biasing means being adjusted to exert different biasing forces onsaid balance means, whereby movement of said sensing means through onepart of its stroke effects pivoting of said balance means about oneaxis, and movement of said sensing means through another part of itsstroke effects pivoting of said balance means about the other axis; asingle control means associated with said housing, said control meanshaving a casing means and a single displaceable actuator extendingoutside said casing means, said actuator being operatively connected tosaid balance means; and

g. said control means having a first control mode at a first position ofsaid actuator and a second control mode at a second position of saidactuator, whereby pivoting of said balance means about one of said axeseffects movement of said actuator through said first position andpivoting of said balance means about the other of said axes effectsmovement of said actuator through said second position so thatadjustment of said biasing means effects adjustment of said controlmodes.

16. A control device as defined in claim 15 wherein:

a. said balance means includes first and second sides;

and

b. said stop means are associated with said first and second sides.

17. A control device as defined in claim 16 wherein:

a. said balance means is a balance plate;

b. said stop means include a first portion and a second portion;

c. said stop means of said first portion include a plurality of stopsspaced apart from each other to define said first axis; and

d. said stop means of said second portion include a plurality of stopsspaced apart from each other to define said second axis.

18. A control device as defined in claim 17 wherein:

a. said first portion of said stop means is associated with said firstside of said balance plate; and

b. said second portion of said stop means is associated with said secondside of said balance plate.

19. A control device as defined in claim 15 wherein said control meansis a microswitch.

20. A control device as defined in claim 15 wherein said first controlmode is an actuation mode'and said second control mode is a deactuationmode.

21. A control device as defined in claim 15 wherein said actuator isoperatively connected to said balance means by an actuating post and aresilient means, said resilient means effecting a lost motion connectionbetween said balance means and said control means.

22. A control device comprising:

A. a housing;

b. a chamber in said housing;

0. a sensing means defining a wall of said chamber, said sensing meansbeing moveable through a stroke;

d. a balance plate, said sensing means being coupled to said balanceplate;

e. stop means cooperating with said balance plate to define first,second and third axes, said stop means including a low pressure part, ahigh pressure part and a pivotal part, said first axis passing throughsaid low pressure part and said pivotal part of said stop means saidsecond axis passing through said high pressure part and said pivotalpart of said stop means, said third axis passing through said highpressure part and said low pressure part, said pivotal part of said stopmeans being spaced from said third axis;

f. a pair of biasing means, at least one of which being adjustable,operatively coupled to said balance plate and adjusted to exertdifferent biases, whereby movement of said sensing means through oneportion of its stroke effects pivoting of said balance plate about saidfirst axis and movement of said sensing means through another portion ofits stroke effects pivoting of said balance plate about said secondaxis;

g. a control means associated with said housing, said control meanshaving an actuation means effectively connected to said balance plateapproximately on said third axis, whereby small displacements of saidbalance plate at said pivotal part of said stop means are nottransmitted to said actuation means.

23. A control device as defined in claim 22 wherein:

a. said actuation means includes a resilient means attached to saidbalance plate;

b. said actuation means further includes an actuating post between saidresilient means and said control means; and

c. said resilient means includes an extension thereon which is directedaway from said pivotal part of said stop means and toward said midpoint.

24. A control device comprising:

a. a housing;

b. a chamber in said housing;

c. a sensing means displaceable through a stroke,

which means defines a wall of said chamber;

d. a balance beam means having first and second ends;

e. a recess in said balance beam means in the region of at least one ofsaid ends;

f. a plurality of stop means co-operating with said balance beam means,at least one of said stop means co-operating with said recess;

g. said stop means defining first and second fulcrums about which saidbalance beam means pivots;

h. a pair of biasing means at least one which being adjustable and eachhaving lines of force acting on said balance beam means, the line offorce of one of said pairs passing through said first fulcrum and theline of force of the other of said pairs passing through said secondfulcrum;

i. control means operatively coupled to said balance beam means;

j. whereby displacement of said sensing means through one portion of itsstroke effects pivoting of said balance beam means about said firstfulcrum and displacement of said sensing means through another portionof its stroke effects pivoting of said balance beam means about saidsecond fulcrum.

25. A control device as defined in claim 24 wherein both biasing meansof said pair are adjustable.

26. A control device comprising:

a. a housing;

b. a chamber in said housing;

c. a displaceable sensing means defining a wall of said chamber;

(1. a balance means having first and second sides, said sensing meansbeing operatively coupled to said balance means;

e. stop means associated with both said first and second sides of saidbalance means to define first and second axes about which said balancemeans pivots;

f. a pair of adjustable biasing means opposing displacement of saidsensing means in one direction;

g. a pair of rotatable screw means, each of said rotatable screw meansbeing associated with one of said biasing means for adjusting the biasthereof;

h. said pair of rotatable screw means having mutually overlappingportions thereon;

i. a control means operatively coupled to said balance means;

j. whereby displacement of said sensing means through one part of itsstroke effects pivoting of said balance means about said first axis anddisplacement of said sensing means through another part of its strokeeffects pivoting of said balance means about said second axis.

27. A control device comprising:

a. a housing;

b. a chamber in said housing;

c. a displaceable diaphragm means defining a wall of said chamber;

d. a biasing means opposing displacement of said diaphragm means in onedirection;

e. said diaphragm means engaging a piston displaceable within a cylindermember;

f. means for centering said piston with respect to said cylinder, saidcentering means including a means for pivotally coupling said piston tosaid biasing means; and

g. said diaphragm including an annular convolution thereon, theformation of said convolution being by chamber pressure and beingfacilitated by the pivotal freedom of said piston.

28. A control device as defined in claim 1 including a resilient meansbetween said control means and said balance means, said resilient meansbeing sufficiently weak to effect a lost motion connection between saidbalance means and said control means during the pivotal movement of saidbalance means about both of said axes.

29. A control device as defined in claim 1:

a. wherein said pair of biasing means is a pair of compressible coilsprings;

b. including a guide means associated with each spring, each guide meansalso being connected to said housing at a connection point;

c. each connection point being associated with one of said springs andlocated at that part of said housing most remote from said oneassociated spring.

30. A control device as defined in claim 2 including:

a. a pair of rotatable screw means each of which is associated with oneof said biasing means for adjusting the bias thereof;

b. said pair of rotatable screw means having mutually overlapingportions thereon.

31. A control device as defined in claim 15, wherein each of saidbiasing means has a line of force acting on said balance means, saidbiasing means being positioned with respect to said balance means suchthat the line of force of one of said biasing means passes through oneof said axes at all positions of said balance means and the line offorce of the other of said biasing means passes through the other ofsaid axes at all positions of said balance means.

32. A control device as defined in claim 15 including a resilient meansbetween said actuator and said balance means, said resilient means beingsufficiently weak to effect a lost motion connection between saidbalance means and said actuator as said actuator moves between its firstand second positions.

33. A control device as defined in claim 15 including:

a. a pair of rotatable screw means each of which is associated with oneof said biasing means for adjusting the bias thereof;

b. said pair of rotatable screw means having mutually overlapingportions thereon.

34. A control device as defined in claim 15:

a. wherein said sensing means is a diaphragm;

b. wherein said diaphragm engages a piston;

c. said piston being displaceable within a cylinder member;

d. including means for centering said piston with respect to saidcylinder, said centering means including a means for pivotally couplingsaid piston to said biasing means; and

e. said diaphragm including an annular convolution thereon, saidconvolution being formed by pressure and being effective to center saidpiston within said cylinder.

35. A control device as defined in claim 18, wherein each of saidbiasing means has a line of force acting on said balance plate, saidbiasing means being positioned with respect to said balance plate suchthat the line of force of one of said biasing means passes through oneof said axes at all positions of said balance plate and the line offorce of the other of said biasing means passes through the other ofsaid axes at all positions of said balance plate.

36. A control device as defined in claim 22 wherein said first andsecond axes nearly intersect each other in the region of said pivotalpart.

37. A control device as defined in claim 22 wherein said actuation meansis effectively connected to said balance plate approximately at themidpoint between said hige pressure part and said low pressure part onsaid third axis.

38. A control device comprising:

a. a housing;

b. a chamber in said housing;

0. a sensing means defining a wall of said chamber,

said sensing means being displaceable through a stroke;

d. a balance means having first and second sides, said sensing meansbeing operatively coupled to said balance means;

e. stop means cooperating with both said first and second sides of saidbalance means to define first and second axes about which said balancemeans pivots, said stop means including a low pressure part, a highpressure part, and a pivotal part, said first axis passing through saidlow pressure part and said pivotal part of said stop means, said secondaxis passing through said high pressure part and said pivotal part ofsaid stop means, said pivotal part being spaced from a line passingthrough said high pressure part and said low pressure part.

f. a pair of biasing means, at least one of which being adjustable andeach having a line of force acting on said balance means, said biasingmeans being positioned with respect to said balance means such that theline of force of one of said pair passes through said first axis at allpositions of said balance means and the line of force of the other ofsaid pair passes through said second axis at all positions of saidbalance means;

g. a control means operatively coupled to said balance means;

h. whereby displacement of said sensing means through one part of itsstroke effects pivoting of said balance means about said first axis anddisplacement of said sensing means through another part of its strokeeffects pivoting of said balance means about said second axis.

39. A control deviceas defined in claim 38 wherein said first and secondaxes nearly intersect each other in the region of said pivotal part.

40. A control device comprising:

a. a housing;

b. a chamber in said housing;

c. a sensing means defining a wall of said chamber, said sensing meansbeing displaceable through a stroke;

d. a balance means having first and second sides, said sensing meansbeing operatively coupled to said balance means;

e. stop means cooperating with both said first and second sides of saidbalance means to define first and second axes about which said balancemeans pivots, said stop means including a low pressure part, a highpressure part, and a pivotal part, said first axis passing through saidlow pressure part and said pivotal of said stop means, said second axispassing through said high pressure part and said pivotal part of saidstop means, said pivotal part being spaced from a line passing throughsaid high pressure part and said low pressure part;

a pair of adjustable biasing means coupled with said balance means, saidbiasing means being adjusted to exert different biasing forces on saidbalance means, whereby movement of said sensing means through one partof its stroke effects pivoting of said balance means about one axis, andmovement of said sensing means through another part of its strokeeffects pivoting of said balance means about the other axis; g. a singlecontrol means associated with said housing, said control means having acasing means and a single displaceable actuator extending outside saidcasing means, said actuator being operatively connected to said balancemeans; and

h. said control means having a first control mode at a first position ofsaid actuator and a second control mode at a second position of saidactuator, whereby pivoting of said balance means about one of said axeseffects movement of said actuator through said first position andpivoting of said balance means about the other of said axes effectsmovement of said actuator through said second position so thatadjustment of said biasing means effects adjustment of said controlmodes.

41. A control device as defined in claim 40 wherein said first andsecond axes nearly intersect each other in the region of said pivotalpart.

42. A control device comprising:

a. a housing;

b. a chamber in said housing;

0. a sensing means defining a wall of said chamber, said sensing meansbeing displaceable through a stroke;

d. a balance means having first and second sides, said sensing meansbeing operatively coupled to said balance means;

e. stop means associated with both said first and second sides of saidbalance means to define first and second axes about which said balancemeans pivots;

a pair of biasing means, at least one of which being adjustable, eachbiasing means being elongated and each having a line of force acting onsaid balance means, the line of force of each biasing means coincidingwith the longitudinal axis thereof, said biasing means being positionedwith respect to said balance means such that the line of force of one ofsaid pair passes through said first axis at all positions of saidbalance means and the longitudinal axis of the other of said pair passesthrough said second axis at all positions of said balance means,

g. a control means operatively coupled to said balance means;

h. whereby displacement of said sensing means through one part of itsstroke effects pivoting of said balance means about said first axis anddisplacement of said sensing means through another part of its strokeeffects pivoting of said balance means about said second axis.

' 43. A control device comprising:

a. a housing;

b. a chamber in said housing;

c. a sensing means defining a wall of said chamber, said sensing meansbeing displaceable through a stroke;

(1. a balance means having first and second sides, said sensing meansbeing operatively coupled to said balance means;

e. stop means associated with both said first and second sides of saidbalance means to define first and second axes about which said balancemeans pivots;

f. said stop means including a plate disposed in said housing above saidbalance means, a wall disposed in said housing below said balance means,a plurality of spherical members extending from both said first and saidsecond sides of said balance means, said members of said first sidebeing adapted to eni. whereby displacement of said sensing means throughone part of its stroke effects pivoting of said balance means about saidfirst axis and displacement of said sensing means through another partof its stroke effects pivoting ofsaid balance means about said secondaxis.

1. A control device comprising: a. a housing; b. a chamber in saidhousing; c. a sensing means defining a wall of said chamber, saidsensing means being displaceable through a stroke; d. a balance meanshaving first and second sides, said sensing means being operativelycoupled to said balance means; e. stop means associated with both saidfirst and second sides of said balance means to define first and secondaxes about which said balance means pivots; f. a pair of biasing means,at least one of which being adjustable and each having a line of forceacting on said balance means, said biasing means being positioned withrespect to said balance means such that the line of force of one of saidpair passes through said first axis at all positions of said balancemeans and the line of force of the other of said pair passes throughsaid second axis at all positions of said balance means; g. a controlmeans operatively coupled to said balance means; h. whereby displacementof said sensing means through one part of its stroke effects pivoting ofsaid balance means about said first axis and displacement of saidsensing means through another part of its stroke effects pivoting ofsaid balance means about said second axis.
 2. A control device asdefined in claim 1 wherein both biasing means of said pair areadjustable.
 3. A control device as defined in claim 1 wherein: a. saidbalance means is a balance plate; b. said stop means includes a firstportion and a second portion; c. said stop means of said first portionincludes a plurality of stops spaced apart from each other to definesaid first axis; and d. said stop means of said second portion includesa plurality of stops spaced apart from each other to define said secondaxis.
 4. A control device as defined in claim 3 wherein: a. said firstportion of said stop means is associated with said first side of saidbalance plate; and b. said second portion of said stop means isassociated with said second side of said balance plate.
 5. A controldevice as defined in claim 1 wherein said control means is amicroswitch.
 6. A control device as defined in claim 5 wherein saidmicroswitch is a single pole, double throw microswitch.
 7. A controldevice as defined in claim 1 wherein: a. said housing has first andsecond ends; b. an inlet means communicates with said chamber, saidinlet means being disposed in said first end; and c. an adjusting meansis disposed at said second end and is accessible from the exterior ofsaid housing.
 8. A control device as defined in claim 1 wherein each ofsaid biasing means is elongated, the longitudinal axis of one of saidbiasing means passing through said first axis, the longitudinal axis ofthe other of said biasing means passing through said second axis.
 9. Acontrol device as defined in claim 1 wherein said stop means include: a.a plate disposed in said housing above said balance means; b. a walldisposed in said housing below said balance means; c. a plurality ofprotrusions extending from both said first and said second sides of saidbalance means, said protrusions from said first side being adapted toengage said wall, said protrusions from said second side being adaptedto engage said plate.
 10. A control device as defined in claim 9 whereinsaid protrusions are formed by a plurality of spherical members, some ofwhich have a first part extending from said first side of said balancemeans and others of which have a second part extending from said secondside of said balance means.
 11. A control device as defined in claim 10wherein said balance means includes a plurality of holes in which saidspherical members are affixed, whereby parts of said spherical membersextend outwardly from said balance means.
 12. A control device asdefined in claim 1: a. wherein said sensing means is a diaphragm; b.wherein said diaphragm engages a piston; c. said piston beingdisplaceable within a cylinder member d. means for centering said pistonwith respect to said cylinder, said centering means including a meansfor pivotally coupling said piston to said biasing means; and e. saiddiaphragm including an annular convolution thereon, said convolutionbeing formed by pressure and being effective to center said pistonwithin said cylinder.
 13. A control device as defined in claim 1 whereinsaid stop means include: a. a first set of protrusions disposed in saidhousing apart from and below said balance means, said first set beingadapted to engage said first side of said balance means; and b. a secondset of protrusions disposed in said housing apart from and above saidbalance means, said second set being adapted to engage said second sideof said balance means.
 14. A control device as defined in claim 13wherein said protrusions are formed bY spherical members.
 15. A controldevice comprising: a. a hollow housing; b. a sensing means displaceablethrough a stroke, said sensing means dividing said housing into asensing chamber and a control chamber; c. a balance means in saidcontrol chamber operatively connected to said sensing means; d. aplurality of stop means co-operating with said balance means to define apair of axes about which said balance means pivots; e. a pair ofadjustable biasing means coupled with said balance means, said biasingmeans being adjusted to exert different biasing forces on said balancemeans, whereby movement of said sensing means through one part of itsstroke effects pivoting of said balance means about one axis, andmovement of said sensing means through another part of its strokeeffects pivoting of said balance means about the other axis; f. a singlecontrol means associated with said housing, said control means having acasing means and a single displaceable actuator extending outside saidcasing means, said actuator being operatively connected to said balancemeans; and g. said control means having a first control mode at a firstposition of said actuator and a second control mode at a second positionof said actuator, whereby pivoting of said balance means about one ofsaid axes effects movement of said actuator through said first positionand pivoting of said balance means about the other of said axes effectsmovement of said actuator through said second position so thatadjustment of said biasing means effects adjustment of said controlmodes.
 16. A control device as defined in claim 15 wherein: a. saidbalance means includes first and second sides; and b. said stop meansare associated with said first and second sides.
 17. A control device asdefined in claim 16 wherein: a. said balance means is a balance plate;b. said stop means include a first portion and a second portion; c. saidstop means of said first portion include a plurality of stops spacedapart from each other to define said first axis; and d. said stop meansof said second portion include a plurality of stops spaced apart fromeach other to define said second axis.
 18. A control device as definedin claim 17 wherein: a. said first portion of said stop means isassociated with said first side of said balance plate; and b. saidsecond portion of said stop means is associated with said second side ofsaid balance plate.
 19. A control device as defined in claim 15 whereinsaid control means is a microswitch.
 20. A control device as defined inclaim 15 wherein said first control mode is an actuation mode and saidsecond control mode is a deactuation mode.
 21. A control device asdefined in claim 15 wherein said actuator is operatively connected tosaid balance means by an actuating post and a resilient means, saidresilient means effecting a lost motion connection between said balancemeans and said control means.
 22. A control device comprising: a. ahousing; b. a chamber in said housing; c. a sensing means defining awall of said chamber, said sensing means being moveable through astroke; d. a balance plate, said sensing means being coupled to saidbalance plate; e. stop means cooperating with said balance plate todefine first, second and third axes, said stop means including a lowpressure part, a high pressure part and a pivotal part, said first axispassing through said low pressure part and said pivotal part of saidstop means said second axis passing through said high pressure part andsaid pivotal part of said stop means, said third axis passing throughsaid high pressure part and said low pressure part, said pivotal part ofsaid stop means being spaced from said third axis; f. a pair of biasingmeans, at least one of which being adjustable, operatively coupled tosaid balance plate and adjusted to exert different biases, wherebymovement of said sensing means through one portIon of its stroke effectspivoting of said balance plate about said first axis and movement ofsaid sensing means through another portion of its stroke effectspivoting of said balance plate about said second axis; g. a controlmeans associated with said housing, said control means having anactuation means effectively connected to said balance plateapproximately on said third axis, whereby small displacements of saidbalance plate at said pivotal part of said stop means are nottransmitted to said actuation means.
 23. A control device as defined inclaim 22 wherein: a. said actuation means includes a resilient meansattached to said balance plate; b. said actuation means further includesan actuating post between said resilient means and said control means;and c. said resilient means includes an extension thereon which isdirected away from said pivotal part of said stop means and toward saidmidpoint.
 24. A control device comprising: a. a housing; b. a chamber insaid housing; c. a sensing means displaceable through a stroke, whichmeans defines a wall of said chamber; d. a balance beam means havingfirst and second ends; e. a recess in said balance beam means in theregion of at least one of said ends; f. a plurality of stop meansco-operating with said balance beam means, at least one of said stopmeans co-operating with said recess; g. said stop means defining firstand second fulcrums about which said balance beam means pivots; h. apair of biasing means at least one which being adjustable and eachhaving lines of force acting on said balance beam means, the line offorce of one of said pairs passing through said first fulcrum and theline of force of the other of said pairs passing through said secondfulcrum; i. control means operatively coupled to said balance beammeans; j. whereby displacement of said sensing means through one portionof its stroke effects pivoting of said balance beam means about saidfirst fulcrum and displacement of said sensing means through anotherportion of its stroke effects pivoting of said balance beam means aboutsaid second fulcrum.
 25. A control device as defined in claim 24 whereinboth biasing means of said pair are adjustable.
 26. A control devicecomprising: a. a housing; b. a chamber in said housing; c. adisplaceable sensing means defining a wall of said chamber; d. a balancemeans having first and second sides, said sensing means beingoperatively coupled to said balance means; e. stop means associated withboth said first and second sides of said balance means to define firstand second axes about which said balance means pivots; f. a pair ofadjustable biasing means opposing displacement of said sensing means inone direction; g. a pair of rotatable screw means, each of saidrotatable screw means being associated with one of said biasing meansfor adjusting the bias thereof; h. said pair of rotatable screw meanshaving mutually overlapping portions thereon; i. a control meansoperatively coupled to said balance means; j. whereby displacement ofsaid sensing means through one part of its stroke effects pivoting ofsaid balance means about said first axis and displacement of saidsensing means through another part of its stroke effects pivoting ofsaid balance means about said second axis.
 27. A control devicecomprising: a. a housing; b. a chamber in said housing; c. adisplaceable diaphragm means defining a wall of said chamber; d. abiasing means opposing displacement of said diaphragm means in onedirection; e. said diaphragm means engaging a piston displaceable withina cylinder member; f. means for centering said piston with respect tosaid cylinder, said centering means including a means for pivotallycoupling said piston to said biasing means; and g. said diaphragmincluding an annular convolution thereon, the formation of saidconvolution beinG by chamber pressure and being facilitated by thepivotal freedom of said piston.
 28. A control device as defined in claim1 including a resilient means between said control means and saidbalance means, said resilient means being sufficiently weak to effect alost motion connection between said balance means and said control meansduring the pivotal movement of said balance means about both of saidaxes.
 29. A control device as defined in claim 1: a. wherein said pairof biasing means is a pair of compressible coil springs; b. including aguide means associated with each spring, each guide means also beingconnected to said housing at a connection point; c. each connectionpoint being associated with one of said springs and located at that partof said housing most remote from said one associated spring.
 30. Acontrol device as defined in claim 2 including: a. a pair of rotatablescrew means each of which is associated with one of said biasing meansfor adjusting the bias thereof; b. said pair of rotatable screw meanshaving mutually overlaping portions thereon.
 31. A control device asdefined in claim 15, wherein each of said biasing means has a line offorce acting on said balance means, said biasing means being positionedwith respect to said balance means such that the line of force of one ofsaid biasing means passes through one of said axes at all positions ofsaid balance means and the line of force of the other of said biasingmeans passes through the other of said axes at all positions of saidbalance means.
 32. A control device as defined in claim 15 including aresilient means between said actuator and said balance means, saidresilient means being sufficiently weak to effect a lost motionconnection between said balance means and said actuator as said actuatormoves between its first and second positions.
 33. A control device asdefined in claim 15 including: a. a pair of rotatable screw means eachof which is associated with one of said biasing means for adjusting thebias thereof; b. said pair of rotatable screw means having mutuallyoverlaping portions thereon.
 34. A control device as defined in claim15: a. wherein said sensing means is a diaphragm; b. wherein saiddiaphragm engages a piston; c. said piston being displaceable within acylinder member; d. including means for centering said piston withrespect to said cylinder, said centering means including a means forpivotally coupling said piston to said biasing means; and e. saiddiaphragm including an annular convolution thereon, said convolutionbeing formed by pressure and being effective to center said pistonwithin said cylinder.
 35. A control device as defined in claim 18,wherein each of said biasing means has a line of force acting on saidbalance plate, said biasing means being positioned with respect to saidbalance plate such that the line of force of one of said biasing meanspasses through one of said axes at all positions of said balance plateand the line of force of the other of said biasing means passes throughthe other of said axes at all positions of said balance plate.
 36. Acontrol device as defined in claim 22 wherein said first and second axesnearly intersect each other in the region of said pivotal part.
 37. Acontrol device as defined in claim 22 wherein said actuation means iseffectively connected to said balance plate approximately at themidpoint between said high pressure part and said low pressure part onsaid third axis.
 38. A control device comprising: a. a housing; b. achamber in said housing; c. a sensing means defining a wall of saidchamber, said sensing means being displaceable through a stroke; d. abalance means having first and second sides, said sensing means beingoperatively coupled to said balance means; e. stop means cooperatingwith both said first and second sides of said balance means to definefirst and second axes about which saId balance means pivots, said stopmeans including a low pressure part, a high pressure part, and a pivotalpart, said first axis passing through said low pressure part and saidpivotal part of said stop means, said second axis passing through saidhigh pressure part and said pivotal part of said stop means, saidpivotal part being spaced from a line passing through said high pressurepart and said low pressure part. f. a pair of biasing means, at leastone of which being adjustable and each having a line of force acting onsaid balance means, said biasing means being positioned with respect tosaid balance means such that the line of force of one of said pairpasses through said first axis at all positions of said balance meansand the line of force of the other of said pair passes through saidsecond axis at all positions of said balance means; g. a control meansoperatively coupled to said balance means; h. whereby displacement ofsaid sensing means through one part of its stroke effects pivoting ofsaid balance means about said first axis and displacement of saidsensing means through another part of its stroke effects pivoting ofsaid balance means about said second axis.
 39. A control device asdefined in claim 38 wherein said first and second axes nearly intersecteach other in the region of said pivotal part.
 40. A control devicecomprising: a. a housing; b. a chamber in said housing; c. a sensingmeans defining a wall of said chamber, said sensing means beingdisplaceable through a stroke; d. a balance means having first andsecond sides, said sensing means being operatively coupled to saidbalance means; e. stop means cooperating with both said first and secondsides of said balance means to define first and second axes about whichsaid balance means pivots, said stop means including a low pressurepart, a high pressure part, and a pivotal part, said first axis passingthrough said low pressure part and said pivotal of said stop means, saidsecond axis passing through said high pressure part and said pivotalpart of said stop means, said pivotal part being spaced from a linepassing through said high pressure part and said low pressure part; f. apair of adjustable biasing means coupled with said balance means, saidbiasing means being adjusted to exert different biasing forces on saidbalance means, whereby movement of said sensing means through one partof its stroke effects pivoting of said balance means about one axis, andmovement of said sensing means through another part of its strokeeffects pivoting of said balance means about the other axis; g. a singlecontrol means associated with said housing, said control means having acasing means and a single displaceable actuator extending outside saidcasing means, said actuator being operatively connected to said balancemeans; and h. said control means having a first control mode at a firstposition of said actuator and a second control mode at a second positionof said actuator, whereby pivoting of said balance means about one ofsaid axes effects movement of said actuator through said first positionand pivoting of said balance means about the other of said axes effectsmovement of said actuator through said second position so thatadjustment of said biasing means effects adjustment of said controlmodes.
 41. A control device as defined in claim 40 wherein said firstand second axes nearly intersect each other in the region of saidpivotal part.
 42. A control device comprising: a. a housing; b. achamber in said housing; c. a sensing means defining a wall of saidchamber, said sensing means being displaceable through a stroke; d. abalance means having first and second sides, said sensing means beingoperatively coupled to said balance means; e. stop means associated withboth said first and second sides of said balance means to define firstand second axes about which said balance means pivots; f. a pair ofbiasiNg means, at least one of which being adjustable, each biasingmeans being elongated and each having a line of force acting on saidbalance means, the line of force of each biasing means coinciding withthe longitudinal axis thereof, said biasing means being positioned withrespect to said balance means such that the line of force of one of saidpair passes through said first axis at all positions of said balancemeans and the longitudinal axis of the other of said pair passes throughsaid second axis at all positions of said balance means, g. a controlmeans operatively coupled to said balance means; h. whereby displacementof said sensing means through one part of its stroke effects pivoting ofsaid balance means about said first axis and displacement of saidsensing means through another part of its stroke effects pivoting ofsaid balance means about said second axis.
 43. A control devicecomprising: a. a housing; b. a chamber in said housing; c. a sensingmeans defining a wall of said chamber, said sensing means beingdisplaceable through a stroke; d. a balance means having first andsecond sides, said sensing means being operatively coupled to saidbalance means; e. stop means associated with both said first and secondsides of said balance means to define first and second axes about whichsaid balance means pivots; f. said stop means including a plate disposedin said housing above said balance means, a wall disposed in saidhousing below said balance means, a plurality of spherical membersextending from both said first and said second sides of said balancemeans, said members of said first side being adapted to engage saidwall, said members of said second side being adapted to engage saidplate; g. a pair of biasing means, at least one of which beingadjustable and each having a line of force acting on said balance means;h. a control means operatively coupled to said balance means; i. wherebydisplacement of said sensing means through one part of its strokeeffects pivoting of said balance means about said first axis anddisplacement of said sensing means through another part of its strokeeffects pivoting of said balance means about said second axis.